Principles of Ocular Surgery Flashcards
1
Q
What are the essential items required for performing ophthalmic surgery?
A
Well trained nurses - familiar with patient preparation and management for ophthalmic cases
Comfortable stool or chair (arm/arm rest ideally)
Adjustable operating table
Magnification (loupes or operating microscope depending on procedure)
Illumination
Positioning devices (wedges, sandbags etc)
Surgical kit
Suture materials and disposable items (drapes etc)
2
Q
What are the two main types of surgical ophthalmic kits that should be available?
A
Adnexal (eyelid and TEL surgery)
Corneal/intraocular kit
Enucleations can use general surgery kit
3
Q
List the equipment you would find in an eyelid/adnexa kit.
A
Bard Parker No 3 scalpel handle
Adson thumb forceps 1x2 teeth
Fixation forceps - e.g Bishop-Harman
Plain dissecting forceps - (iris type)
Bennett Cillia forceps
Stevens Tentotomy scissors curved
Ribbon scissors straight blunt/blunt
Halstead Mosquito artery forceps x 4
Well’s artery forceps curved x2
Castroviejo needle holders curved without catch
Foster-Gillies needle holder
Towel Clamps
Gallipot
Eyelid Speculum
Chalazion clamp
Lid plate
4
Q
What instruments would you find in a corneal/intraocular surgery kit?
A
Towel clamps
Beaver scalpel handle
Bishop-Harman forceps (delicate)
Colibri forceps (corneal)
Harms tying forceps
Well’s artery forceps (curved)
Castroviejo needle holder curved
Westcott’s tenotomy scissors
Steven tenotomy scissors
Small plain scissors (for canthotomy)
Castroviejo spring action scissors (curved)
Barraquer eyelid speculum
5
Q
What instruments would you find in an enucleation kit?
A
Adson thumb forceps
Bard Parker No 3 scalpel handle
Metzenbaum scissors curved 5.5”
Stevens tenotomy scissors
Towel clamps
Landolt enucleation scissors
Allis tissue forceps
Halstead mosquito forceps
Crile artery forceps
Eyelid speculum
6
Q
How are ophthalmic instruments designed to be used by the surgeon?
A
Designed to be manipulated with minimal movement from surgeon - upper arms and forearms remain still whilst hands and wrists used to adjust the instruments.
7
Q
What differences are there in design of ophthalmic instruments compared to normal surgical instruments?
A
Weight - lightweight (material e.g titanium or presence of holes within them to minimise weight)
Pencil grip - majority designed to be held in pencil grip, similar diameter to pencil to help with this
Tactile feedback - when using operating microscope cannot see instrument handles just tips so ridges, knurling of handles or flattening are useful. Held prevent slipping and encourage correct finger placement.
Dulled/dark finish - reduces scatter of refracted light under microscope
Sprung - allows hand or wrist position to not have to be altered to reopen insrument
Pin stop - may be present to prevent excessive pressure on closure leading to damage of delicate tips
Operate in only one direction e.g corneal scissors, often flat handled whilst those requiring rotation e.g needle holders may have rounded handles.
Lock may be present - grasping of delicate needle without continuation of pressure
Length - microsurgical instruments shorter usually 100mm rather than 120-140mm of normal instruments so do not touch bottom of microscope during procedure.
Surgical tips small and delicate.
8
Q
How should ophthalmic instruments be cared for?
A
Dedicated nurses to clean/pack who understand instruments
Wiped with cellulose sponges during surgery to remove debris during surgery.
Gauze swabs not in same kit - may catch and bend tips of instruments
Blood/contaminants rinsed off before they dry
Open spring instruments for cleaning
Ultrasonic cleaner or gentle sponge to wipe instruments - do not use scrubbing brush
Rinse in instrumentation lubrication fluid from time to time.
Check with magnification every few uses - ensure tips of forceps and needle holders meet properly and no bends.
9
Q
How should ophthalmic instruments be stored?
A
Specially designed boxes which keeps them separate from each other and secure.
Silicone rubber fingers to prevent instruments contacting each other ideal.
Rubber tips on sharp or delicate parts
Sterilised and chemical indicator strip within box.
Box then wrapped in paper or linen drape and in self seal sterilisation bag.
10
Q
What are the main types of eyelid speculum and what is their purpose?
A
Barraquer and Castroviejo
Used to retract the lids to enhance exposure of the conjunctiva, cornea and globe.
Cats/small dogs - barraquer
Larger dog breeds - castroviejo as stronger instrument
Blades tucked under lids in closed position and gently opened to required position.
11
Q
What is the purpose of tissue forceps?
A
Grasping eyelid skin, conjunctiva or corneal wound edges.
12
Q
Why do microsurgical forceps e.g calibri forceps have angled tips?
A
Angled tips = help to maintain surgical visibility down the operating microscope
13
Q
When are tying platforms on forceps useful?
A
Found close to the tip of the forceps to allow suture material to be grasped without it being damaged by the instrument tips themselves.
14
Q
What is the benefit of Von Graefe forceps over forceps with 1x2 teeth (e.g Bishop-Harman)
A
Teeth on forceps can cause button hole tears in conjunctiva which can be quite delicate.
Von Graefe = 10-14 fine teeth allowing greater tension and holding ability with reduced risk of conjunctival tearing/damage.
Von Graefe = too large for microsurgery
15
Q
What are cilia forceps used for?
A
Smooth blunt ends for grasping and removing aberrant lashes.
Bennett’s cilia = rounded tips to prevent accidental damage to lid margins
Whitfield cilia = flat oblique tips
16
Q
Why are teeth required on forceps for the cornea, sclera and limbus? What are the 2 types
A
Fibrous tissue to grasp
Perpendicular (dog toothed) or splayed (tips ending outwards)
Splayed = better grasping on smooth surfaces.
17
Q
What are mosquito forceps used for?
A
Haemostasis and stabilisation of parts of the globe (e.g limbus or TEL)
18
Q
What types of knives are used in ophthalmic surgery?
A
Bard Parker handle and blades (No 15 and 11) - adnexal/TEL
Beaver handle and blades (No 64, 65 and 67) - conjunctival/corneal incisions
Keratomes - either to fit beaver handle or separate disposable instruments = diamond shaped blades for full thickness corneal surgery e.g cataract surgery. Provide incision of accurate witdth e.g 3.2mm for introduction of phacoemulsification needle
Restricted depth knives - corneal surgery e.g superficial keratectomy/removal of corneal sequestra. Blade with raised button or stop so that can only be inserted to a fixed depth within the cornea (300um for example) - safer for beginners to use but very expensive.
Lamellar blades - useful for dissecting cornea at even depth, round ended and angled to ensure same plane of cutting.
19
Q
What types of scissors may be used in ophthalmic surgery?
A
Steven’s tenotomy (curved or straight) -eyelid/conjunctival dissection
Metzenbaum - general eyelid skin dissection
Landolt enucleation scissors - steeply curved blade to follow curvature of globe.
Corneal/corneoscleral scissors e.g castroviejo/westcotts have springs rather than rings for holding to allow greater control of cutting + held in pencil grip, smaller handles with delicate tips.
20
Q
What should determine the type of needle holder you use? What type of needle holders are seen?
A
Size of needle = size of needle holders
Corneal needle holders shaped similar to scissors but have rounded rather than flat handles and a spring action so they are open when resting.
Tips can be straight or curved.
May or may not have locking mechanism (no locking for microsurgical procedures as opening the lock can jar the tips affecting precise positioning of the needle)
Pin stop to prevent excessive compression of handles.
Gillies and Hager-Meyer style needle holders for larger suture material e.g eyelid surgery.
21
Q
What is a lacrimal dilator use for?
A
Small pencil like instrument = locate nasolacrimal puncta prior to cannulation. Used for diagnostic purposes for nasolacrimal flushing as well as during surgery for micro and imperforate nasolacrimal puncta.
22
Q
What is a chalazion clamp used for?
A
Has 2 plates - one open and one solid and a screw to tighten and fix instrument to lid.
Helps with excision of eyelid masses, ectopic cilia removal, cryosurgery for distichia.
Stabilises lid, maintains haemostasis and protects underlying globe from inadvertent damage.
23
Q
When is a Jaeger lid plate used?
A
Smooth plate to stabilise eyelid so that incision can be made against the plate, also protects underlying globe.
24
Q
What are chalazion curettes used for?
A
Small sharp curettes used to remove inspissated material from chalazion and are best employed in conjunction with a chalazion clamp.
25
When are callipers used?
Used for precise measurements of tissues
e.g entropion/ectropion surgery, advancement skin flaps
26
What are the two methods of sterilisation employed for ophthalmic instruments?
Chemical (cold)
Heat
Autoclave under pressure at temperature of 121 degrees routinely used with drying cycle.
Ethylene oxide also efficient and prevents blunting of surgical blades which occurs with repeat steam autoclaving (but health and safety so rarely encountered these days).
27
What factors should affect suture material choice?
Anatomic features of the tissue
Tensile strength of the tissue
Duration sutures need to remain in place
Type of suture pattern to be used
Whether sutures will need removal
28
What is the most common suture material used in veterinary ophthalmology and why? What are its pros and cons?
Vicryl (Polyglactin) - multifilament
Pros:
Easy to handle (no memory, less inclined for over tightening and cheese wiring than nylon, absorbable (no need to remove sutures, softer and less irritating than nylon.
Cons:
Greater tissue reaction than nylon
Knots are relatively large and less secure and cannot be rotated into the suture mark
Only available down to 9/0 in regular vicryl
29
What are the pros and cons of using nylon in ophthalmic surgery?
Nylon = monofilament
Pros = minimal tissue reaction (particularly important in axial cornea) retains tensile strength for very long periods, more elastic properties (less likely to break down with trauma), secure knots which can be cut down and buried in the suture track. Available down to 11/0
Cons - difficult to handle as has memory and very slippery, tends to cling in any moisture.
Easy to overtighten and cheesewire which may cause astigmatism.
Knots irritating if not buried
May need removal under GA post operatively.
30
What size suture material would you use for tarsorrhaphy or skin sutures in larger breeds?
4-0
31
What size suture material would you use for skin sutures e.g entropion or nictitans gland surgery?
6-0
32
What size suture material would you use for conjunctival suturing?
8-0
33
What size suture would you use for corneal surgery?
8-0 to 10-0
34
What is the usual needle diameter to suture ratio and what advantage does this have?
5:1 ratio
Advantage that can bury suture knot within needle tract if required
35
What are the 4 different types of needle for microsurgical sutures?
Taper point, Reverse cutting, Cutting, Spatula
36
What are the features of a cutting needle and what is its use?
Sharp point and sides - triangle in cross section
Traumatic to tissue
Difficult to accurately control depth
Use = skin only
37
What are the features of a reverse cutting needle and what is its use?
Sharp point and sides - upside down triangle in cross section
Traumatic to tissue
Difficult to accurately control depth
Use = skin only
38
What are the features of a taper point needle and what is its use?
Sharp point but smooth sides
Little tissue trauma
Not sharp enough for skin
Use limited to conjunctiva
39
What are the features of a spatula tipped needle and what is its use?
Designed for use in lamellar tissue as remain in same plane and thus accurate placement is possible
Used for cornea
40
What suture patterns are used in ophthalmic surgery and what is the aim of suturing?
Simple interrupted
Simple continuous - corneal graft/transpositions
Bootlace - cornea following phacoemulsification
Aim = align and compress tissue for healing to occur
Minimal compression required for conjunctiva
Accurate even compression for cornea
41
What types of drape are there for ophthalmic surgery?
Both linen and disposable drapes can be used
Linen = extraocular procedures generally as not water resistant
Can have sticky back drapes to adhere to skin around eye and can be folded back under eyelids so preferred for intraocular surgery.
Specialised drapes for intraocular surgery (e.g phaco) exist and include a pouch in the drape or separate bag to collect excess irrigating fluid.
42
What types of swabs should be used for ophthalmic surgery?
Soft and lint free (no woven/gauze swabs as any fibres left in ocular area could be irritating)
Cellulose spears advised for microsurgery (e.g keratectomy, corneal/conjunctival grafts and any other intraocular procedures) - safe to dab on cornea and can absorb intraocular fluids as necessary.
43
What size nasolacrimal cannulas should be available when performing ocular surgery.
0.91mm (pink) and 0.76mm (blue)
44
What types of irrigating fluids are there?
Sterile saline - cleansing prior to surgery, flushing cornea/conjunctival sac and checking nasolacrimal patency. Not advised to use if risk of intraocular penetration (e.g removal of corneal foreign body)
Hartmanns/lactated ringers - more appropriate irrigating solution if risk of corneal perforation as more similar in consistency to aqueous humour as contains buffers such as bicarbonate as well as sodium/chloride which make them physiologically more similar. Non irritating and minimal damage to intraocular tissues e.g endothelium.
45
When are contact lenses typically used in ophthalmology?
Used ton provide ocular comfort post procedure
E.g post SCCED debridement, corneal healing - protect delicate epithelium from being rubbed by eyelids during blinking.
Also used for spastic entropion - relieve blepharospasm.
Baush and Lomb Purevision 2 plano lenses are favoured.
46
When are collagen shields used in ophthalmology?
Can be used as a bandage during healing of corneal ulcer or post superficial keratectomy - need to be rehydrated fully before inserting into the eye. Dissolve in a few days.
47
When may hyaluronic acid sub dermal fillers be used?
Temporary correction of entropion - young puppies/elderly cats where desirable to avoid anaesthesia.
48
What level of magnification is suitable for lid and nictitans surgery?
2-4x (loupes)
49
What level of magnification should be used for corneal, conjunctival and intra-ocular procedures?
Minimum 4-5x (all way up to 25x) - operating microscope best
50
What are the advantages and disadvantages of using loupes for magnification?
Binocular magnification with range of magnifications (generally 2-7x, wobbles after 4.5x so max would generally want)
Have varying focal length and quality of image
Light source mounted or not
Spectacle or head mounted types
Advantages - direction of view easily changes, good for adnexal surgeries, PDT, enucleation etc, cheap (compared to microscope)
Disadvantages - fixed image (focal distance), wobbles at high magnification, moderate magnification
51
What are the advantages and disadvantages of the operating microscope?
Advantages - excellent image quality, magnifying capability can be varied during procedure, no wobble, built in co-axial illumination, XY can be varied
Disadvantages - Cost, fixed position, instruments introduced into surgical field blind, size, requires considerable practice to use
52
What considerations are there for surgeon positioning for ophthalmic surgery?
Mostly wrist/hand movements - sitting down with arm rest often more comfortable
Height of seat adjustable - not cramped but not feet dangling
If using loupes surgeon comfortable at fixed focal length
53
What considerations are there for patient positioning for ophthalmic surgery?
Eyelid surgery - lateral recumbency head elevated or sternal recumbency head elevated (bilateral/compare symmetry) - face parallel with table
Intraocular surgery - aim to have cornea horizontal (dorsal recumbency)
54
How would you clip a patient for ophthalmic surgery?
Prep - outside theatre
If unilateral procedure fellow eye protected with lubricating gel/ointment (e.g HyloNight, soft white paraffin or Viscotears, carbomer 940)
Lubricating gel also applied to other eye to protect whilst clipping and reduce hair deposition into conjunctival sac.
Scissors to cut eyelashes - KY jelly to help lashes stick to scissor blades
Clipping (essential for lid surgery, may not be performed for intraocular - aiming to reduce irritation, if so sterile drape tucked under eyelids)
Sharp fine clipper blades (no bigger than No 40) - area clipped 2cm bigger than expected surgery site
Lateral canthus clipped for procedures that may require lateral canthotomy
Clip in direction of fur growth to reduce irritation.
Stray hairs removed with hand held vacuum or sticky roller.
55
How would you prepare the surgical site for ophthalmic surgery.
Non sterile gloves on
Sterile saline on lint free swabs can be used to gently wipe any remaining hairs.
Povidone iodine solution for disinfection of surgical site (conjunctiva - gram +ve bacteria) - UNLESS PERFORATION/RUPTURE
Dilutions made with sterile saline or distilled water.
1:50 solution for conjunctival sac 5-10ml syringe - contact time 3 mins
Sterile cotton buds or cellulose spears dipped in 1:50 used to remove any debris from conjunctival sac
Then flushed with sterile saline or Hartmanns - at least 10mls
Local skin 1:10 dilution on lint free swabs
If bilateral patient can be turned and cleansed eye protected by clean dry lint free swab.
When ready to operate final skin preparation 1:10 in theatre
Prediluted solutions can be kept in sterile saline fluid bags and kept for 1-2 weeks
56
What types of systemic analgesia may be used?
Majority of ophthalmic patients - NSAID will provide sufficient analgesia
Opiates sometimes required - methadone, buprenorphine, oral tramadol
Pre-emptive analgesia - more stable GA and recovery, reduce anaesthetic dose, reduce risk of hypoxia, hypercapnia and acidosis from pain hyperventilation.
Vocalisation can increase IOP so if pain related needs adressing
Helps avoid self mutilation
Pre-medication with both NSAID and opioid in combination with anxiolytivc e.g ACP often undetaken.
57
What scenarios may topical anaesthesia be used for?
Diagnostic e.g assess spastic vs anatomic entropion
Minor surgical procedures - e,g diamond burr, ulcer debridement, biopsy sampling, removal of superficial foreign bodies
In conjunction with regional or general anaesthesia for analgesia (reduce amount of systemic agents required e.g superficial keratectomy)
Must never be used as an analgesic treatment - corneal toxicity, one off dose only to avoid epithelial damage.
58
What are the most common topical anaesthesia agents used?
0.5% Proxymetacaine - minims single use vials
Duration 45-60 mins, stings less than tetracaine on application and faster acting
0.5-1% Tetracaine/amethocaine - not stored in fridge, slower onset but longer duration of action than proxymetacaine
Lidocaine 2% - occasionally used topically but mostly for nerve blocks
59
What regional anaesthesia techniques can be implemented in small animals for ophthalmic surgery?
Retrobulbar block (for enucleations and occasionally intraocular surgery) - analgesic effect and reduced haemorrhage
Auriculopalpebral/surpaorbital - usually horses
60
What agents are used for retrobulbar blocks?
Bupivicaine (alone or in combination with lidocaine)
0.5% bupivacaine lasts 5-10 hours whereas only 45-60 minutes for 2% lidocaine although latter faster onset.
Combined injection has benefit of rapid efficacy and longer lasting.
61
Which cranial nerves does the retrobulbar block affect?
III - occulomotor
IV - trochlear
V - trigeminal
VI - abducens
Plus ciliary ganglion
Injections either intraconal (into muscle space) or extraconal (latter potentially safer as injection is further away from the globe but higher volumes required, potentially increased toxicity/multiple injections)
62
What is the preferred approach for retrobulbar injections?
Inferior-temporal palpebral technique
1.5 inch 22 gauge spinal needle bent to 20 degree angle
Placed at inferior orbital rim and inserted through lower lid at junction of its middle and temporal third.
Advanced gently until popping sensation felt (this is needle entering orbital fascia)
Needle direction then changed slightly more dorsal and nasal towards apex of orbit and advanced 1-2cm
Volume 2ml commonly injected - equal parts 2% lidocaine and 0.5% bupivicaine.
63
What signs of efficacy are there for retrobulbar nerve blocks?
Efficacy indicated by pupil dilation, central rotation of globe, inhibition of ocular movements.
64
What are the complications of retrobulbar nerve blocks?
Globe perforation
Haemorrhage
IV injection
Optic nerve damage
Intrathecal injection - seizures, respiratory arrest
65
What anaesthetic drug should not be used alone due to its effect on raising IOP?
Ketamine
66
What procedures commonly done pre-anaesthetic should be done with care due to risk of increasing IOP?
Jugular venepuncture
Restraint for catheter placement
Pre-medication with agents that can induce vomiting should be avoided (e.g alpha 2 agonists)
67
What is the oculocardiac reflex?
Mediated by trigeminal and vagus nerve
Stimulus to eye causes bradycardia (asystole in very extreme cases)
68
Which groups of patients may need more tailored general anaesthetic plans for ophthalmic surgery?
Brachycephalics- pre-oxygenation, recovery in oxygen cage. Use of maropitant/omeprazole to reduce risk of reflux.
Young/geriatric patients - ability to metabolise drugs may be compromised and limitations in general homeostasis.
Diabetics - titrated insulin levels, provision of dextrose infusions and frequent blood glucose assessment.
69
What are the 3 key concepts of a good anaesthetic?
Provide narcosis (unconciousness)
Analgesia
Muscle relaxation
70
Why should care be taken with the ET tube on recovery in ophthalmic patients?
Coughing/gagging can increase IOP and put any wounds under considerable tension.
71
When may neuromuscular blocking agents be used?
Routinely used for intraocular procedures (cataract surgery, removal of luxated lenses etc) although may also be useful for corneal surgeries since eye position maintained centrally and there is guaranteed globe immobility.
Extraocular muscles are also fully relaxed so no pressure is exerted on posterior globe or vitreous.
72
Why must an anaesthetist ensure the patient is fully anaesthetised before using neuromuscular blocking agents? How is the degree of muscle relaxation measured and what is essential if using these techniques.
Agents do not cross blood-brain barrier so have no effect on consciousness.
Train of 4 used to measure degree of relaxation
Mechanical ventilators essential.
73
What are the most widely used neuromuscular blocking agents?
Pancuronium
Vacuronium
Atracurium
Neostigmine = most common reversing agent
74
What are the principles of when to refer cases for ocular surgery?
Equipment and instrumentation available to you - e.g operating microscope requirement for intraocular surgery
Level of experience with the condition to be treated
Owner finances and ability to travel
Owner expectations
75
What are the principles of ocular microsurgery?
Adequate restraint - GA generally although few procedures e.g conjunctival biopsy/nasolacrimal flushing can be performed wiht topical anaesthesia +/- sedation
Correct surgical instruments for procedure
Suitable magnification - adnexal surgery (loupes), corneal/intraocular (microscope)
Appropriate delicate surgical technique - limited tissue trauma
Subdivided into techniques to incise (separate tissue), tissue stabilisation (grasping), tissue re-alignment (suturing)
76
What techniques to incise are suitable for the cornea?
Sharp debridement
No 64 Beaver blade at edges of ulcer
Lamellar keratectomy - fixed depth blade, smooth single stroke with even pressure
Full thickness incision - stab incision with pointed blade or keratome
77
What technique to incise is used for eyelid skin?
Eyelid skin tensed and stabilised then incised in one fluid movement using No 15 Bard-Parker scalpel blade
Multiple short tracks to be avoided as wound edges will be ragged increasing inflammation and potential scarring as well as making more accurate suturing difficult.
Use of Jaeger lid plate or surgeons finger to protect globe from inadvertent damage
Once skin incision has been made fully sharp scissors may be used to cut through rest of tissue to be excised.
78
What technique should be used for incising conjunctiva?
E.g for harvesting conjunctival grafts and during transconjunctival enucleation.
Best made sharply with a blade to outline desired area and correct depth before continuing blunt dissection with steven's or westcott's tenotomy scissors.
79
When may blunt dissection be used in ophthalmic procedures?
Undermining skin for blepharoplasty procedures
Dissect in correct plane for conjunctival grafts
80
What instruments are typically used for tissue stabilisation?
Forceps - rely on creating enough friction to resist the inherent forces of the tissue and those of the surgeon working adjacent to the forceps.
Too little friction - tissue slips through forceps
Re-grasping = damage and inflammation
Used either to immobilise tissue or to mobilise it.
Choose correct instrument with appropriate teeth for job essential.
81
What type of forceps should be used for grasping the conjunctiva?
Delicate teeth - grasp close to site of incision to reduce slippage
82
What type of forceps are designed to grasp cornea?
Colibri forceps - only free edges created by incision, ulcer edge or laceration should be grasped
83
How can the globe be stabilised during ophthalmic surgery?
Muscle relaxant anaesthesia to prevent rolling down of eye
Stay sutures to rotate eye up and stabilise 4-0 vicryl or similar with haemostats at end of the suture
Fine mosquito forceps in conjunctiva close to limbus - two pairs
84
What are the aims of tissue alignment?
Re-establish normal function
Ensure clear visual axis
Achieve good cosmetic appearance
Achieved by combination of wound alignment and compression
85
What does wound re-alignment rely upon?
Sutures placed perpendicular to wound margin (oblique = movement of wound edges delaying healing and increasing scarring. Badly placed sutures = aqueous leaking in cornea)
Adequately apposes all tissue layers and not just the superficial layer
Multiple fine closely spaced sutures - ensures wound compression
Rule of bisection during closure
86
What is the dangle technique and why is it used?
Used for picking up micro-needles for corneal surgery
Suture grasped with tying platform of forceps 1-2cm away from needle and latter allowed to dangle down onto drape
Needle holders can then correctly pick up the needle without need for readjustment.
Should not use fingers to pick up the needle.
87
What action is used by the surgeon when performing ophthalmic surgery to pass the needles through tissue?
Rolling wrist action rather than trying to force needle through tissues. Allows needle to follow is own angle of cuvature.
88
What are the 2 suture patterns commonly seen with eyelid procedures?
Rule of bisection - Hotz Celsus entropion procedure where 2 incisions of unequal length - prevents lip of tissue forming at one end. First suture placed in centre of wound, 2nd and 3rd then bisecting the 2 halves and then so on. Allows even distribution and good apposition.
Figure of 8 - Perfect alignment of lid margin (eyelid lacerations/mass removals) - required for proper function of the lid. If step in leading edge allows mucus/debris to accumulate and spread of tear film compromised.
Also important no suture placed so close to lid margin that ends/knots rub cornea.
2 layer closure of eyelid wound associated with better comfort.
89
Do conjunctival incisions always need suturing?
Small incisions will heal quickly without suturing (e.g cojunctival biopsy)
Larger defects however require closure - 8-0 vicryl simple continuous and buried knots
90
When may a tarsorraphy be used?
Can be temporary or permanent.
Partially close eyelids over cornea to provide protection.
May be used:
Following conjunctival graft/contact lens placement
Post proptosis replacement
OR permanent solution for lagophthalmic patients (inability to close eyelids fully)/macropalpebral fissure
91
How is a temporary tarsorraphy performed?
Sutures should not be full thickness through eyelid so as to rub cornea
Horizontal mattress sutures 4-0 on cutting needle placed through eyelid margin at lateral canthus
Stents may be used to prevent suture cutting into eyelid skin.
92
What type of tarsorraphy may be used in patients with a macropalpebral fissure?
Permanent tarrsoraphy procedure - can be performed medially or laterally
Medial is usual in brachycephalic patients
Lateral sometimes used for correcting macropalpebral fissures
Relevant portion of eyelid margin is excised prior to opposing the cut edges with simple interrupted sutures.
93
What are the most common reasons for requiring corneoconjunctival surgery?
Ulceration (>50% stromal depth)
Trauma - lacerations
Foreign bodies
Opacification and scarring affecting vision
Feline sequestrum
Neoplasia/Dermoids
94
List some of the procedures that can be performed on the cornea.
Keratotomy
Diamond burr keratectomy
Direct corneal suturing
Superficial keratectomy
Conjunctival flaps and grafts
Corneoconjunctival transposition
FB removal
Cyanoacrylate adhesives
Non ocular graft material
Penetrating and lamellar keratoplasties
95
What is a keratotomy? What is the difference between this and a keratectomy? Give an example of when it may be performed.
Small cuts made into cornea - either in punctate or linear grid pattern
Non healing corneal ulcers = indication SCCED
Can be done under topical anaesthesia alone or under sedation/GA if fractious patient
23 or 25 gauge needle to perform - perforate epithelium and anterior stroma after debridement
Keratotomy = small cuts into cornea
Keratectomy = removal of portion of cornea
96
When is a diamond burr keratotomy used?
Used to remove loose epithelium and stimulate healing in SCCEDs
Performed after cotton bud debridement under local anaesthesia and well tolerated conscious.
Safer to use than needle keratotomy and results in negligible scarring.
97
When may direct corneal suturing be performed?
Following traumatic lacerations and planned corneal incisions
98
What are the 3 objectives that must be fulfilled for effective repair of full thickness corneal lacerations and planned incisions via direct corneal suturing?
Wound must be sealed without incarceration of uveal tissue
Anterior chamber must be re-established
Visual axis should remain clear keeping the eye sighted
99
How should corneal sutures be placed? What depth?
Placed perpendicular to the wound
Should be placed approx 2/3rd corneal thickness and pass through to opposite side of wound at same depth as in the first side (vertical wounds)
Oblique wounds entry and exit sites need adjusting to ensure smooth surface on wound closure.
100
How can correct suture placement and seal formation be checked during corneal suturing?
Once tied suture should leave good apposition and watertight seal.
Check with cellulose sponge - gently press around area, if leakage of aqueous visible than not formed tight enough seal and sutures should be replaced.
101
What suture material is used for corneal suturing and how are the knots placed?
Polyglactin (vicryl)
Square knots - double overhand throw followed by 2 or 3 single throws in alternate directions
If nylon chosen - triple overhand throw + 3 single throws and knot rotated into suture track.
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When may mattress sutures be used in corneal suturing?
Areas of marked tension or if cornea is holding sutures poorly
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When may cruciate sutures be used in corneal suturing?
To reduce number of knots required and if commenced within depths of wound knot can be tied within wound hence burying without need to rotate suture.
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When may continuous sutures be used in corneal suturing?
Repairing limbal incisions and finishing grafts once simple interrupted cardinal sutures placed - advantage of speed, fewer knots and ability to spread tension evenly across wound prior to closure.
Clean lacerations may also be repaired with this method.
Drawback - rely on one or 2 knots to hold entire length
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When may simple interrupted sutures be used in corneal suturing?
Used mostly - laceration repair, graft placement etc
Advantage of breakage of one suture does not mean complete failure.
Main disadvantage = uneven spread of tension along wound margins, slower to place, more knots as potential irritants.
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When is a superficial keratectomy performed?
How is it performed?
Either in isolation or combined with grafting - excision of cornea (epithelium and stroma)
Thickness of stroma removed depends on condition being treated.
As rule if keratectomy leads to more than 1/2 to 2/3rd of stomal depth removed then defect should be covered with conjunctival graft or corneoconjunctival transposition.
Indications- dermoids, chronic or recurrent corneal erosions, corneal/limbal neoplasia, corneal sequestrum, superficial foreign bodies. (Very occasionally pannus or pigmentary keratitis)
Diseased area outline with initial incision
Desired depth estimated with slit lamp prior to surgery and should be sufficient to remove base of diseased cornea.
Restricted depth knife (250-300um) makes initial incision easier but could also used No 64 Beaver blade (more flexibility with depth of incision)
Edge of section to be removed then grasped with Colibri forceps
Dissection plane within stroma should remain in same parallel lamellae throughout keratectomy - use of lamellar blade makes easier.
Dissected stroma then removed and any remaining tags removed with scissors.
Forceps should only grasp area to be removed and not healthy cornea adjacent.
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When are conjunctival grafts typically used? How are they performed?
Used for management of deep or large corneal ulcers, desmetocoeles and for perforated corneas with and without iris prolapse over lacerations which have been sutured but require additional support.
Consist of either bulbar (typically) or palpebral conjunctival mucosa with epithelium and connective tissue.
Provide additional support for weakened cornea without risk of host rejection.
Contain blood vessels and lymphatics to encourage healing as well as antibacterial, antiviral and antiprotease/collagenase effects.
Transplants antibodies, serum, alpha 2 macroglobulin immediately into damaged cornea.
Systemic AB's can reach site through conjunctival blood vessels
Fibrovascular and deeper layer of conjunctiva = fibroblasts and collagen to rebuild stroma.
Usually result in varying sizes/degrees of corneal scars which reduce central vision.
Made by undermining a section of bulbar conjunctiva and then suturing directly to cornea.
1st prepare defect by superficial keratectomy or direct suture
Eyelid speculum and lateral canthotomy useful to increase exposure
Small incision made into conjunctiva 1-2mm from limbus with scissors (e. Westcotts)
Separate from tenon's capsule (layer separating conjunctiva from sclera - this layer should not be included)
Incision then extended to around 90/120 degrees around eye following curvature of limbus
Conjunctiva freed from underlying tissue by blunt dissection
Ideal flap semi-transparent.
Conjunctiva then pulled down over ulcer (advancement flap) or rotated into defect (pedicle flap)
Pedicle flaps preferred for central defects/lager defects.
Flap can be trimmed to fit defect and once in place sutured with simple interrupted pattern or cardinal 3-4 sutures then simple continuous.
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What are the indications for corneoconjunctival transposition grafts?
Similar indications as for conjunctival - deep ulcers, desmetocoeles , perforated corneas, following superficial keratectomies if deep.
Preferred over conjunctival grafts for central lesions as less central scarring and therefore better visual outcome.
With CCT portion of clear cornea, usually dorsal to lesion is transplanted into the lesion whilst attached to bulbar conjunctiva - advancement flap with cornea as well as conjunctiva.
1. Recipient corneal bed should be prepared - diseased tissue removed using superficial or deep keratectomy.
2. Graft prepared with 2 diverging corneal incisions with No 64 Beaver blade of restricted depth knife and extended to limbus
3. Pedicle of anterior corneal stroma and epithelium separated from deeper stroma of limbus with corneal lamellar dissector. Ideal thickness 50% corneal depth. Once limbus transversed with the blade or sharp scissors the conjunctival portion of graft is then mobilised with small tenotomy scissors
4. Conjunctival graft should be wider than recipient site to allow for graft shrinkage
5. Corneal edges of graft are sutured using simple interrupted pattern
Temporary tarsorraphy may help tamponade the graft bed, prevent blinking and reduce exposure - particularly helpful in brachycephalic patients.
Corneal portion of graft clears over first few weeks post op, conjunctival portion takes several months to clear.
Limbal region transposed to cornea will always remain apparent.
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How can corneal foreign bodies be classified?
Penetrating = embedded within the stroma (partial thickness) - no fibrin in anterior chamber
Perforating = protruding into anterior chamber (full thickness) - fibrin in the anterior chamber or on cornea, pupil often misshapen (dyscoria), possibly some hyphaema.
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How may non perforating foreign bodies be removed?
Surface/superficial - topical anaesthesia and saline flush + cotton bud (sterile) or dry surgical spear/foreign body spud.
Penetrating:
GA + careful eye preparation
DO NOT GRASP with forceps - risk of pushing foreign body deeper and inadvertently causing perforation.
One or 2x 23-25 gauge needles - impale object perpendicular to its trajectory and gently rotated out of cornea in opposite direction to entry.
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How may perforating corneal foreign bodies be removed?
Removal more complicated if perforating FB
Depending on size/shape may be approached from anterior cornea or from inside via anterior chamber
If perforating FB removed via cornea may be useful to place horizontal mattress suture beforehand across corneal defect allowing you to quickly suture post removal and reduce aqueous loss and resultant uveitis.
Worst case scenario may end up doing keratectomy and then direct suturing +/- graft placement.
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When may cyanoacrylate adhesives (tissue glue) be used?
Can be used to seal small corneal defects e.g small partial lacerations, pin point desmetocoeles, small diameter deep stromal ulcers.
Not to be used in cases of infected ulcers or for peforations.
Epithelium able to grow under glue and plug spontaneously extruded.
Ophthalmic N-butyl cyanoacrylate = most common.
N-butyl removes exothermic reaction
Instantly polymerises when in contact with fluid therefore cornea must be completely dry to apply (achieved using canned air)
Painted on layer by layer using 30G needle
Plug should not emerge beyond level of normal cornea = otherwise acts like FB
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What are lamellar and penetrating keratoplasties?
Donor corneal tissue from same species (homologous)
Lamellar keratoplasty - partial thickness (epithelium and stroma)
Penetrating keratoplasty - full thickness button of cornea
Fresh cornea preferable but frozen acceptable
Tend to get more vascularisation with full thickness procedures than in man
Risk of rejection as not host tissue
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What are the 2 most commonly performed intraocular surgeries?
Cataract surgery (phacoemulsification or extracapsular cataract extraction)
Removal of luxated lenses (intracapsular lens extraction)
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What equipment is required as standard for cataract surgery?
Operating microscope
Positioning aids (dorsal recumbency generally - corneas horizontal)
Phacoemulsification machine + tubing + handpiece and tip
Intraocular irrigation fluid
Irrigation/Aspiration handpiece
Surgical drapes
Intraocular kit
Cataract kit - keratome or diamond knife, utrata capsule forceps, hydrodissection cannulae, vannus scissors, nucleus rotator/phaco cleaver, callipers, IOL introducer and forceps
Blue colour capsule dye
Viscoelastic material
Intraocular lens + inserter and foceps
23G needle with insulin syringe - for capsulorhexis
Cellulose spears
Vitrectomy handpiece and disposables
Suture material - polyglactin 910 or nylon - 8/0 - 10/0
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What are the basic steps of phacoemulsification?
1. Surgical entry to anterior chamber via keratome
2. Blue colour dye for delineating anterior lens capsule
3. Anterior chamber maintained with viscoelastics (frequent top ups)
4. Anterior capsulohexis - continuous circular capsulohexis (shearing/tearing force to enter anterior capsule)
5. Hydrodissection/hydrodelineation (for immature cataracts)
6. Nuclear sculpting - 1 and 2 handed techniques
7. Irrigation/aspiration of soft cortical material
8. Capsular bag polishing
9. IOL implantation
10. Closure of corneal wound
11. Re-inflation of globe
(Vitrectomy occasionally necessary)
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What steps are generally performed when assessing if patient suitable candidate for cataract surgery?
Full physical exam - general health
Full ophthalmic exam including gonioscopy (not at risk of primary glaucoma)
Ultrasound of globe - assess for retinal detachments, no other concurrent pathology etc
Electroretinography - ensure functional retina
Also consider patient - will they be of the right temperament for post op care/follow ups
Assess owner also - finances, ability to carry out aftercare, availability for rechecks, realistic expectations
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What is measured frequently post cataract surgery as a post op precaution?
IOP measured frequently post op - ensuring no glaucoma spike occurring.
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What is the typical aftercare and medications for a patient post phacoemulsification/cataract surgery?
Topical medications - steroids, antibiotics, NSAID's and mydriatics (usually very intense tx for 1 month, most on drops for at least 6 months and some patients indefinitely)
Systemic - antibiotics, NSAID
Kept quiet with lead exercise only
Elizabethan collar initially
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What is the general success rate for cataract surgery and what are the potential complications seen?
85-95% success rate - lower than in humans (much thicker lens)
Complications - ongoing uveitis, ulceration, posterior capsular opacification, glaucoma, retinal detachment, intraocular haemorrhage
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If an intraocular lens is placed with cataract surgery what type of vision do these patients typically have? What about if no lens placed?
Usually close/mid range vision ok
No lens placed have long distance vision only and may struggle seeing objects up close.
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What are the basic steps for extracapsular lens extraction?
Another technique for cataract surgery
1. Corneal groove performed - partial thickness 150 degree incision in clear cornea 1mm from limbus
2. One end of groove perforated with pointed No 67 Beaver blade or keratome
3. Groove cut along with corneal scissors
4. Stay suture or colibri forceps open incision
5. Capsulorhexis (shear and tensile force to tear apart anterior capsule of lens)
6. Lens loop to remove cataract nucleus
7. Copious flushing to remove cortex and cataract fragments
8. Closure of wound with simple continuous pattern
9. Re-inflation of globe
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What breeds are prone to primary lens luxation? How do they present?
Terriers and Border Collies
Present unilaterally but is bilateral disease
Inherent weakness within lens zonules
Can have either anterior or posterior luxations
DNA testing avaliable
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What are the signs of primary lens luxation?
Acutely painful eye
Corneal oedema
Episcleral and conjunctival hyperaemia
Lens visible in anterior chamber and change in anterior chamber depth
Aphakic cresent (subluxated lens)
Blindness if raised IOP and secondary glaucoma
Iridodonesis and vitreal strands in pupil in fellow eye = partial luxation
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What is the treatment for primary lens luxation?
Anterior lens luxation = urgent lendectomy if visual or potentially visual
(Check IOP, duration of luxation and consensual PLR in other eye, dazzle, menace etc)
<24-36hrs - worth removing lens
>36hrs or blind - worse prognosis
Enucleation if non visual/severe glaucoma
Monitor fellow eye - consider miotics (e.g latanoprost)
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What is the general approach to a subluxated lens?
?Monitor vs removal sometimes debated
Risk of glaucoma both by leaving in but also by removal + risk of retinal detachment
If decide to surgically remove - either intracapsular lens extraction technique or phacoemulsification. (Phaco = lower complications and better prognosis but most require ICLE)
Prostaglandin analogues e.g latanoprost often used to create miotic pupil and keep lens behind iris (but warn can cause microtrauma to iris, narrowing of drainage angle and risk of glaucoma)
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What are the steps for performing intracapsular lens extractions?
1. Corneal groove performed - partial thickeness 150 degree incision in clear cornea 1mm from limbus
2. One end of groove perforated with No 67 Bard Parker blade or keratome
3. Cut along groove with corneal scissors
4. Stay suture or colibri forceps to open incision
5. Lens loops or cryo-extractor to remove entire lens within its capsule
6. Vitrectomy as required (ideally automatic but cellulose spears and sharp scissors can be employed if no vitrectomy machine)
7. Closure of wound with simple continuous pattern
8. Reinflation of globe.
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When may vitrectomies be performed?
Can be necessary during cataract (e.g posterior lens capsule breached) and lens luxation surgeries
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When is vitreoretinal surgery mainly performed?
Mainly for retinal detachments with aim of restoring some vision or preventing total blindness.
Potentially suitable cases - detachments following cataract surgery, lens luxation, chronic lens induced uveitis, retinal dysplasia, collie eye anomaly and trauma.
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When may prophylactic retinopexy be performed?
Used in the second eye if the first has already suffered catastrophic retinal detachment (but not without risk - mainly of causing detachment!)
Laser retinopexy more common than cryosurgery.
Both can be performed transclerally but transpupillary approach preferred using special indirect lenses to be able to visualise areas.
Aim of technique = spot weld the retina over a specific area to attempt to strengthen attachments and reduce risk of detachment.
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What techniques are there for the treatment of existing retinal detachments?
Scleral buckling (indenting sclera to release vitreal tension and allow detached area to scar over)
Pneumatic retinopexy (gases used to tamponade the retina, usually immediately following a pexy procedure
Demarcation/barrier retinopexy - (laser burns to halt progression of a detachment which is linear or small hole/tear)
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With vitrectomies for large retinal tears/detachments what is injected to tamponade the detached retina back into positon?
Once entire vitreous removed perflurocarbon liquid or silicone oil injected, gently unravelling detached retina as required.
Laser then used to weld retina back into position around periphery and randomly over entire surface.
Silicone oil can be left in globe as an artificial vitreous.
If perflurocarbon used (provides better tamponade than silicone oil) then it needs to be replaced by silicone oil.
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What post operative care considerations should there be after an ophthalmic surgery?
Post op - gentle cleaning of surgical area with sterile saline on lint free swabs
Analgesia - usually NSAID +/- opioid pain relief
Topical +/- Systemic medications (ensure O's shown how to correctly apply drops etc for good compliance)
Elizabethan collar to prevent wound interference/rubbing or alternatively could consider use of foot bandages initially for 12-24hrs so if do rub less likely to cause damage. Most likely to rub on recovery so monitor closely and also just after application of topical meds.
Discharge patients with clear written instructions regarding type and frequency of medication, when to recheck and any other requests e.g lead exercise, keeping cats indoors etc.
